With Pekins, since they are good sized ducks, they should do reasonably well with decent shelter and good nutrition.
They'll need to be dry, out of the wind, with plenty of insulation. Getting more specific is tough, since my little spoiled runner duck flock has a couple of members who do not thrive at all below freezing, so they spend much of the winter (New England) in the duckie storm shelter in the walkout basement. It's much easier on me, too!
It's about 40F there, and I don't have to shovel three feet of snow out of their run or shovel a path to feed them. All good.
Now is most certainly the time to think about winter, since you'll want plenty of dry bedding, perhaps enough straw to insulate an area, might try a water warmer (I have one the metal pan sits on, some people get heated buckets).
Frozen water is something to think about - you won't get it often, probably, but it's a bit of a pain if you're not expecting it. Some use pans of hot water to thaw the ice in the morning, some just break the icy top off.
I installed a thermometer with a remote sensor so I could check the indoor duck house temperature without opening the door. That has been helpful in extreme temperatures at both ends.
Watch the ducks. I watched mine and they told me, "book sez we like 20F. book wrong. "
